It is well known to provide a motor vehicle with apparatus often referred to as a stop-start system to automatically stop and start the engine when a number of predefined conditions are found to be present.
Such stop-start systems reduce fuel consumption and emissions by stopping the engine when it would otherwise by unnecessarily idling.
Typically, a number of other components or systems such as, for example and without limitation, a climate control system, an instrument cluster, a brake system and an electric power supply system have a modified operation to provide an appropriate behavior during the various engine operating states.
For example, the loss of engine idling when the engine has been automatically stopped means that power is unavailable for typical engine driven ancillaries e.g. the alternator, vacuum pump, water pump and air conditioning compressor. This lack of power often leads to reduced performance of the associated systems and this loss in performance may be noticeable by an occupant of the motor vehicle.
The most noticeable loss is that associated with the climate control system. To maintain cabin comfort in winter, a source of heat energy must be transferred from the engine to the cabin heater matrix and to maintain cabin comfort in summer, a source of cold refrigerant must be supplied to the evaporator or heat exchanger in the cabin.
As neither is normally possible with the engine stopped, the climate control system often automatically operates in an attempt to maximize the time that acceptable cabin comfort can be maintained by taking mitigating actions such as changing the position of air control flaps and reducing the blower speed. Ultimately, the climate system may request that the engine be automatically restarted to maintain cabin comfort for a longer period, or request that further engine stops be prevented until a range of parameters within the climate system is met. Such parameters may include, in winter, ensuring the engine coolant is sufficiently warm to provide heat to the cabin and, in summer, ensuring that the evaporator is sufficiently cold to prevent the formation of damp or musty smells in the cabin.
In order to maximize stop availability whilst minimizing the impact on cabin climate comfort, an inevitable trade-off must therefore be made by the system designers and this trade-off is likely to be sub-optimal for many vehicle occupants, leading to dissatisfaction with vehicle performance.
It is further known to provide a stop-start enabled motor vehicle with a driver selectable switch, which can be used to de-activate the stop-start system.
However, although such a switch enables a driver to manually deactivate the automatic stop start behavior of the motor vehicle this will result in an unacceptable increase in both fuel consumption and engine emissions.